The present invention relates to the manufacture of intraocular lenses (IOLs) for implantation in an eye. The present invention more particularly relates to an apparatus and method for molding IOLs.
A common and desirable method of treating a cataract eye is to remove the clouded, natural lens and replace it with an artificial IOL in a surgical procedure known as cataract extraction. In the extracapsular extraction method, the natural lens is removed from the capsular bag while leaving the posterior part of the capsular bag (and preferably at least part of the anterior part of the capsular bag) in place within the eye. In this instance, the capsular bag remains anchored to the eye's ciliary body through the zonular fibers. In an alternate procedure known as intracapsular extraction, both the lens and capsular bag are removed in their entirety by severing the zonular fibers and replaced with an IOL which must be anchored within the eye absent the capsular bag. The intracapsular extraction method is considered less attractive as compared to the extracapsular extraction method since in the extracapsular method, the capsular bag remains attached to the eye's ciliary body and thus provides a natural centering and locating means for the IOL within the eye. The capsular bag also continues its function of providing a natural barrier between the aqueous humor at the front of the eye and the vitreous humor at the rear of the eye.
Although there are many different IOL designs, all IOLs have an optic for directing and focusing light on the retina, along with means for anchoring the IOL in the correct position within the eye. In one common IOL design, the anchoring means comprises two resilient filaments called haptics which extend in a curved fashion from opposite sides of the optic. In the so-called “one-piece” IOL design, the haptics are integrally formed with the optic, for example by milling the optic and haptics from a single blank of IOL material. In the so-called “three-piece” design, the haptics are mechanically attached to the optic, typically by inserting an end of the haptic into a respective anchoring hole in the optic. In this design, adhesives are sometimes also used to ensure the haptics are securely attached to the optic.
Three-piece IOL designs are typically more difficult to manufacture due to the added steps required to mechanically anchor the haptics to the optic, and also because adhesives can be difficult to apply and have adverse physiological affects should the adhesive come into contact with the delicate tissues of the eye. There is also the possibility that the mechanical anchoring means may inadvertently cause glare or create other interference with the normal passing of light into the eye through the IOL.
IOLs may be manufactured by molding, milling, lathing, or a combination thereof. Of these manufacturing methods, molding is generally the least expensive method of manufacture and hence more desirable than lathing and/or milling. Prior art molding methods include compression molding, injection molding, and transfer molding, for example. Many of these prior art methods are directed at three-piece IOL designs which suffer from the drawbacks mentioned above. Prior art molding methods of one-piece IOLs also have drawbacks such as the requirement for a number of auxiliary processing steps, as well as difficulty to implement in a high-speed, robust manufacturing process. It would therefore be highly desirable to have an apparatus and method for molding a single-piece IOL design in an inexpensive manner which is adaptable to a high speed production facility.